Many Integrated Circuits (ICs) are powered by an internal regulated voltage source which insures device protection from voltages that may exceed operating specifications if unregulated supplies were used. However, using a regulated supply has a major downfall. That downfall being that the current supplied by the regulated supply may be too limiting during critical operating cycles of a given IC.
For example, in a Dynamic Random Access Memory (DRAM), during active pull up time, a large current spike causes the internal regulated supply to take a sizable dip. This dip in voltage can slow down the operation of the DRAM (i.e. measurements of access time to column address (.sub.t AA) have shown .sub.t AA to slow down by as much as 4 ns on 4 Mbit Drams).
Prior solutions include such ideas as, increasing the current capacity of the regulator or improving the regulator's frequency response both of which have disadvantages. A disadvantage of increasing the current capacity of the regulator is that it requires extra bias current to operate the IC as P-channel power amplifiers require a lot of extra current to turn them on. A disadvantage of improving the frequency response of the regulator is the circuit complexity required.
What is needed is a simple circuit, with no feedback or frequency response considerations to take into account, that will supply the needed current at the proper time.